A GRE quant score of 166 is generally considered good for applicants to physics Ph.D. programs, falling within the mid-90th percentile for physics candidates. While a score below 170 may not be ideal for top theoretical physics programs, it is not a significant barrier, especially for experimental physics applicants. Admissions decisions are based on a comprehensive evaluation of the entire application, including undergraduate grades, research experience, recommendations, and publications. Concerns about the GRE score may be overstated, and applicants are encouraged to manage stress, as the field of science often involves challenges and uncertainties that can be much more demanding than the application process itself.